The pain in the back and neck could be a result of some of the effects nicotine has on your physiology. Nicotine can certainly cause muscle spasticity
and overactivity of nerve firing. There can also be central "brain" effects of nicotine that turn up your sensation of pain that is always there due to arthritis etc.
The most worrisome causes would be related to the possibility of an esophageal or stomach cancer
caused by tobacco use. However this would usually also be associated with weight loss
, loss of appetite, and other symptoms, like nausea, dyspepsia
, change in bowel habits, and abdominal pain